This invention relates to a well pumping system that uses pressurized air and operates simultaneously as a positive displacement pump and as a gas lift pump, to pump well fluids intermitently; and may also be used in combination with other pumping devices such as those disclosed in the copending application Ser. No. 07/311,086, filed Feb. 15, 1989, and in U.S. Pat. No. 4,832,577 issued on May 23, 1989, to pump well fluids continuously, extracting them by suction from the pores of a geologic formation.
In various Civil-Environmental Engineering projects wherein assessment of the ground water quality is to be made, it becomes necessary to collect ground water samples for subsequent chemical analysis. In common practice, ground water samples representing ground water in the pores of a geologic formation are collected from monitoring wells installed in the particular formation. The quality of the ground water samples however, may greately be affected by the presence of stagnant well fluids in the monitoring well. To assure collection of high quality ground water samples, it is required that stagnant well fluids be purged (removed) entirely or partially from the monitoring well prior to sample collection. Depending on the hydrogeologic characteristics of the geologic formation, well purging may become possible by pumping the well dry, or by pumping well fluids equivalent to a specified number of volumes of the stagnant well fluids. Various types of methods/devices are available for purging monitoring wells, for example: air lifting, hand bailers, and bladder pumps. U.S. Pat. Nos. 4,585,060 and 4,489,779 describe in detail a typical bladder pump. Among the disadvantages of all available methods/devices however are, the introduction of undesirable disturbances in the hydrogeologic regime around the well screen, their low pumping rate associated particularly with deep monitoring wells, and their high initial cost.
In similar projects, it is often necessary to extract by suction the fluids from the pores of the geologic formation for site remediation purposes, as required in spills of toxic substances in soils; and for soil stabilization purposes, as often required in foundation engineering problems The existing art, U.S. Pat. No. 4,660,639, and U.S. Pat. No. 4,593,760, employes a suction source that consists of a vacuum pump or an exhaust fan located at the ground surface away from the well screen. Usually, a single suction source is used at a central location connected to the heads of many extraction wells through an extensive piping network which may be susceptible to leaks. Under these conditions, an effective operation for extracting fluids by suction requires air flow control, which in turn may require balancing to assure proper suction distribution to each leg of the network, using a series of air flow meters and regulators. Additionally, if the extracted fluids are ignitable, as often is the case with petroleum product spills, the vacuum pumps must employ explosion-proof motors and nonsparking wheels rendering thus the extraction systems of the existing art expensive.
Therefore, the purpose of the present invention is to provide a pumping system that among its other uses may be used for more efficient and cost effective monitoring well purging, sampling, and extraction of fluids by suction from the pores of a geologic formation.